Spark ignition systems

ABSTRACT

A spark igniter and re-igniter for gas-fired appliances is provided with a normally-closed switch associated with the gas valve and connected across the capacitor of an RC net. This provides a leakage path for the main discharge capacitor when the gas supply is turned off, and prevents damage to the input transformer in the event of a short circuit in the switch by leaving the high-value resistor of the RC net in circuit.

0 United States Patent 11 1 1111 3,904,350

Goble Se t. 9, 1975 [54] SPARK IGNITION SYSTEMS 3,477 797 l 1/1969 Ziclinski et al. 431/256 3 529 9 70 l 4 7 [75] inventor: Arthur Richard Goble, Fareham, Fons at a 31/2 E l d g an Primary ExaminerEdward G. Favors [73] Assignee: Pleasey Incorporated, Melville, NY. Armmey, Agent, or Firm-James J Burke, ll

[22] Filed: Aug. 1, I974 21 Appl. No.: 493,768 [57] ABSTRACT A spark igniter and re-igniter for gas-fired appliances V is provided with a normally-closed switch associated [2%] with the g valve and cmmected across the Capacitor 254 256 of an RC net. This provides a leakage path for the I 1 0 Tc main discharge capacitor when the gas Supply is turned off, and prevents damage to the input trans- [56] References cued former in the event of a short circuit in the switch by UNITED STATES PATENTS leaving the high-value resistor of the RC net in circuit.

3,318,358 5/1967 Potts 431/256 X 3,377,125 4/1968 Zielinski 431 74 6 Claims, 1 Drawing Flgure SPARK IGNITION SYSTEMS BACKGROUND OF THE INVENTION This invention relates in general to electric gas ignition systems such as for use in gas-fired appliances such as stoves. More particularly, the present invention relates to a system having improved safety features.

In one gas ignition system for insuring that gas burners are re-ignited should they become accidentally extinguished, line voltage is applied to a transformer, the output from which charges a main discharge capacitor through a rectifier (e.g. diode). In respect of each of the gas burners for which the re-ignition facility is provided, the system includes a switch with normally-open contacts which are connected at the high voltage end of the transformer circuit in series with a resistor and auxiliary capacitor across the main discharge capacitor. The switch is closed when the gas valve is opened. The junction between this resistor and auxiliary capacitor is connected, on the one hand, to the trigger electrode of a thyristor or other controlled rectifier through a gas discharge device (eg neon tube) and on the other hand to a spark gap associated with a gas burner through the secondary of a spark generating transformer.

In operation of such a system, initial closure of one pair of switch contacts consequent upon the actuation of the gas valve operatively associated with a gas burner completes a circuit for charging the auxiliary capacitor through the series connected resistor, as well as establishing a current path including the spark gap associated with the gas burner. Since the gas burner has yet to be ignited the resistance of this current path is relatively high, so that the voltage across the gas dis charge device effects breakdown thereof and the controlled rectifier is triggered. On triggering of the rectifier, the spark generation transformer having its sec ondary in the aforesaid current path is pulsed to effect ignition of the gas in the spark gap.

Once the burner has ignited the resistance of the current path decreases, and the voltage across the gas discharge device is insufficient to maintain conduction through the device and consequently the SCR will be turned off.

If, however, during operation of the burner the flame should become accidentally extinguished, then once again the initial sequence of operation for gas ignition as described above will be repeated automatically without re-operation of the switch having normally-open contacts.

OBJECTS OF THE INVENTION It is a general object of the present invention to provide a spark ignition system for gas appliances with improved safety features.

Another object of the present invention is to provide a spark ignition system operative to prevent the main discharge capacitor from retaining a charge when the system is off.

A further object of the present invention is to provide a spark ignition system wherein the line transformer is protected in the event of a short circuit.

Various other objects and advantages will become clear from the following description of an embodiment thereof, and the novel features will be particularly pointed out in connection with the appended claims.

THE DRAWING Reference will hereinafter be made to the single accompanying drawing, which is a schematic circuit diagram of an embodiment of the invention.

DESCRIPTION OF EMBODIMENTS According to the present invention there is provided a gas ignition system with a re-ignition facility, comprising a main discharge capacitor arranged to be charged from an a.c. source through a transformer and a rectifier (e.g. diode), a resistor connected in series with an auxiliary capacitor across said main capacitor to form an RC circuit, the junction between the auxiliary capacitor and the resistor being connected on the one hand to a gas discharge device (eg neon device) in the firing circuit of a silicon controlled rectifier, and on the other hand to a circuit including a spark gap and the secondary of a spark generating transformer for producing gas ignition pulses in response to the firing of said controlled rectifier, and switching means operable for completing the gas ignition-re-ignition circuit and operatively associated with a gas valve of a gas burner and having normally-closed contacts which are connected directly across the auxiliary capacitor on the ground or low voltage side of the resistor.

The gas ignition/re-ignition system of the present invention ensures that the switch referred to is always at a safe voltage while the short-circuiting of the nongrounded or high voltage side of the switch to ground still leaves the resistor in circuit across the input transformer, thus avoiding damage to the transformer due to the passage therethrough of excessive current. Additionally, when the switch contacts close upon the turning off of the gas valve, the contacts provide a leakage path for the main discharge capacitor, thereby quickly dissipating the capacitor charge that might otherwise be retained when the ac. supply is switched off.

By way of example, a specific embodiment of the invention will now be described with reference to the accompanying drawing, which shows a circuit diagram of a gas ignition/re-ignition circuit arrangement for use in gas stoves.

Referring to the drawing, the circuit 10 comprises an input transformer 12 having primary winding 14 thereof connectable to an a.c. line supply 16, and having its secondary winding 18 connected to a main discharge capacitor 20 through a diode 22. The main discharge capacitor 20 has connected across it an RC net comprising a resistor 24 in series with an auxiliary capacitor 26. The junction between the two capacitors 20, 26 is connected to ground The junction between the capacitor 26 and resistor 24 is connected, on the one hand, to one side of a neon breakdown device 28 the other side of which is connected to the gate electrode of a silicon-controlled rectifier 30 which is connected in series with primary winding 32 of a spark impulse transformer 34. The junction just referred to is also connected through secondary 36 of the transformer 34 to ground via a spark gap 38 which is associated with a gas burner. In accordance with the invention, a switch 40 operatively associated with the gas valve 41 spindle appertaining to the gas burner has its normally-closed contacts connected across the auxiliary capacitor 26 so that one side of the switch is connected to ground, and the other side of the switch is connected to the junction between the resistor 24 and the auxiliary capacitor 26. It is preferred that an addi tional back-biased diode 42 be provided across primary winding 32 of spark coil 34, as this blocks current flow back to the main capacitor or other circuitry and generally facilitates operation of the triggering circuit.

In operation of the system, the contacts of switch 40 will be opened when the gas valve 41 associated with the gas burner having the spark gap 38 is opened, and as a consequence the auxiliary capacitor 26 will be charged up by the discharge of the main discharge capacitor 20 so that the voltage at the junction between the resistor 24 and the auxiliary capacitor 26 is sufficiently high to cause the neon device 28 to breakdown, thereby triggering the SCR 30, as a consequence of which an ignition pulse is generated by the transformer 34 in response to the discharge of capacitor 20. Once the gas in the spark gap 38 has ignited, the resistance of the current path extending from the junction of the resistor 24 and the auxiliary capacitor 26 to the transformer secondary 36 and spark gap 38 will be reduced so that the voltage at the junction of the resistor 24 and auxiliary capacitor 26 will drop to a level insufi'icient to cause the neon tube 28 to break down. As a consequence, the SCR 30 will be switched off and no further ignition pulses will be produced by the transformer 34.

If, however, during operation of the stove the gas at the spark gap 38 should be accidentally extinguished, then once again the resistance of the current path including the spark gap 38 and secondary winding 36 will be increased to the point where the voltage at the junction between the resistor 24 and the capacitor 26 will rise to cause the neon device 28 to break down and cause re-triggering of the SCR 30 and further impulsing of the spark gap 38.

As will readily be appreciated from the circuit arrangement, the transformer 34 may be provided with a plurality of secondary windings, such as the winding 36 each being associated with a spark gap, such as the gap 38 appertaining to an individual gas burner. Each of these secondary windings, such as the winding 36 will be connected to a junction point between a series connected resistor and auxiliary capacitor, such as the resistor 24 and the capacitor 26 in the drawing. All of these series circuits will be connected across the main discharge capacitor 20. Each of the auxiliary capacitors will have connected across it a switch, such as the switch 40 and these switches will be operatively associated with the respective gas valves appertaining to the gas burners. The SCR 30 will be common to all of the resistor/auxiliary capacitor circuits and each of these circuits will be connected to the trigger electrode of the SCR through its own individual neon tube, such as the neon device 28 in the accompanying drawing.

It will be apparent from the foregoing description of an embodiment of the invention that the switch 40 is grounded on one side and the other side thereof will always be at a low voltage (maximum voltage will be of the order of 80 volts) in view of the interposition of high resistance value resistor 24. This makes for a high degree of safety in operation, and it will also be seen that if the junction side of the switch 40 were to be short-circuited to ground then the high resistance resistor 24 will still remain in series with the secondary 18 of the transformer 12 so that the transformer will not be damaged by short-circuiting of the switch 40. Moreover, the arrangement of the switch whereby one side of the switch is connected to a ground on the stove and the other side of the switch requires a single wire connection is particularly advantageous. Still further, when the line voltage is disconnected from the circuit arrangement, then the normally-closed contacts of the switch 40 complete a leakage path for the capacitor 24 so that during maintenance operations the capacitor will be fully discharged. A still further feature of the embodiment is that no double insulation of the switch 40 is required.

In a typical embodiment of the invention, the diodes 22 and 42 are IN. 4006s, main capacitor 20 has a value of 2.2 pf, auxiliary capacitor 26 has a value of 0.0047 pf, resistor 24 has a value of 150 MO, neon tube 28 is a Hivac A 351 and SCR is a TAG l-400.

Various changes in the details, steps, materials and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as defined in the appended claims.

What is claimed is:

1. Gas flame ignition apparatus comprising:

a transformer having primary and secondary windings;

a spark gap in the path of said gas having one said connected to ground and the other side connected in series with one side of said secondary winding;

a charging circuit comprising a main charging capacitor connectable to an alternating current source through a unidirectional current device, said main charging capacitor being in parallel connection with said primary winding;

a triggering circuit comprising a silicon-controlled rectifier in series with said primary winding and said main charging capacitor and an RC network including a resistor and an auxiliary capacitor in parallel with said main charging capacitor, the junction of said resistor and auxiliary capacitor being connected to the gate electrode of said silicon controlled rectifier through a voltageresponsive breakdown device;

a flame-sensing circuit comprising a connection between the other side of said secondary winding and the junction of said resistor and auxiliary capacitor; and

normally-closed switch means connected across said auxiliary capacitor and to ground, whereby said main charging capacitor is discharged to ground when said apparatus is off.

2. The ignition apparatus as claimed in claim 1, and additionally comprising a gas supply including a valve, opening of said valve acting to open said switch means.

3. The ignition apparatus as claimed in claim 1, and additionally comprising an alternating current transformer in circuit between said source and said charging circuit.

4. The ignition apparatus as claimed in claim 1, wherein said unidirectional current device is a first diode, and additionally comprising a second diode biased oppositely to said first diode and connected across said primary winding.

5. The ignition apparatus as claimed in claim 3, wherein said resistor in said RC network is a high-value resistor.

6. The ignition apparatus as claimed in claim 1, and additionally comprising a plurality of secondary wind ings on said transformer, each said winding in series 6 with one of a plurality of additional spark gaps, each and an additional flame sensing circuit and normally Secondary wmdmg bemg fired by Sald mam closed switch means for each said additional secondary charge capacitor through said silicon controlled rectifier by an additional RC network in parallel with said one RC network and an associated breakdown device, 5

winding and RC network.

UNITED STATE. PA'IENT JFK-IO 3 stem: No. I 3 50 m D:::er1 September 9 1975 Arthur Richard Goble lrventork's) It is certified that error appears in the above-identified patent nzr that said Letters Patent are hereby corrected as shown below:

On the cover page, item 73, Assignee, should read as follows:

Plessey, Incorporated, Melville, New York Column 2 line 52 A period should appear after "ground".

Column 4, line 25: "having one said" should read having one side Signed and Scaled this eighteenth ,D 3) Of No vember 19 75 [SEAL] Arrest.

RUTH C. MASON C. MARSHALL DANN Im'srmg Ofjuer ('nmrm'ssmm'r of Pun'ms and Trademurki 

1. Gas flame ignition apparatus comprising: a transformer having primary and secondary windings; a spark gap in the path of said gas having one said connected to ground and the other side connected in series with one side of said secondary winding; a charging circuit comprising a main charging capacitor connectable to an alternating current source through a unidirectional current device, said main charging capacitor being in parallel connection with said primary winding; a triggering circuit comprising a silicon-controlled rectifier in series with said primary winding and said main charging capacitor and an RC network including a resistor and an auxiliary capacitor in parallel with said main charging capacitor, the junction of said resistor and auxiliary capacitor being connected to the gate electrode of said silicon controlled rectifier through a voltage-responsive breakdown device; a flame-sensing circuit comprising a connection between the other side of said secondary winding and the junction of said resistor and auxiliary capacitor; and normally-closed switch means connected across said auxiliary capacitor and to ground, whereby said main charging capacitor is discharged to ground when said apparatus is off.
 2. The ignition apparatus as claimed in claim 1, and additionally comprising a gas supply including a valve, opening of said valve acting to open said switch means.
 3. The ignition apparatus as claimed in claim 1, and additionally comprising an alternating current transformer in circuit between said source and said charging circuit.
 4. The ignition apparatus as claimed in claim 1, wherein said unidirectional current device is a first diode, and additionally comprising a second diode biased oppositely to said first diode and connected across said primary winding.
 5. The ignition apparatus as claimed in claim 3, wherein said resistor in said RC network is a high-value resistor.
 6. The ignition apparatus as claimed in claim 1, and additionally comprising a plurality of secondary windings on said transformer, each said winding in series with one of a plurality of additional spark gaps, each said secondary winding being fired by said main discharge capacitor through said silicon controlled rectifier by an additional RC network in parallel with said one RC network and an associated breakdown device, and an additional flame sensing circuit and normally closed switch means for each said additional secondary winding and RC network. 